需要一种方法来检查哪些几何点在给定的时间间隔内彼此相距设定距离

Question

所以我有一个名为“船只”的船舶坐标的空间数据库。 它有以下表格：

SHIPS
============
id (serial)
vessel(uuid)
time(timestamp without timezone)
coord(geometry(Point, 4326)

我需要编写一个查询，返回其坐标为X米远的船只，时间间隔为Y。到目前为止我有这个：

SELECT DISTINCT ON (a.vessel, b.vessel) a.vessel, b.vessel 
FROM ships a
INNER JOIN ships b
ON a.vessel = b.vessel
WHERE
ST_DWithin((ST_Transform(a.coord, 3035)),(ST_Transform(b.coord, 3035)), 5000)
AND (EXTRACT (EPOCH FROM(a.time - b.time))) <= 1500
AND (a.vessel != b.vessel);

但是如果我离开a.vessel！= b.vessel约束它总是返回null，如果我删除它，结果在两列上都是相同的容器。

Answer 1

您在联接中使用了错误的条件：

SELECT DISTINCT ON (a.vessel, b.vessel) a.vessel, b.vessel 
FROM ships a
INNER JOIN ships b
ON ST_DWithin((ST_Transform(a.coord, 3035)),(ST_Transform(b.coord, 3035)), 5000)
WHERE
(EXTRACT (EPOCH FROM(a.time - b.time))) <= 1500
AND (a.vessel != b.vessel);